Pyrithione compounds are typical compounds used in anti-Malassezia-furfur agents, anti-fouling agents for fishing nets, or antiseptics. However, pyrithione (2-mercaptopyridine-N-oxide) is a highly irritating compound, and further, it is not stable chemically, and gradually converts into a disulfide body. Therefore, there are few actual cases in which pyrithion itself is used in industrial bactericides. For instance, pyrithione antimicrobial agents are generally known as sodium pyrithione, zinc pyrithione, and copper pyrithione. These metal pyrithiones exhibit very high antimicrobial activities, but they have respective drawbacks. Sodium pyrithione, for example, is unstable in a dried state, and it is difficult to handle. Zinc pyrithione and copper pyrithione are poor in solvent solubility, such that even mixtures of them with other industrial bactericides were unsuccessful in attempts to enhance antimicrobial power. In addition, all these pyrithione compounds have a simple structure with no substituents on their respective rings.
As an example of antiseptics intended to resolve the foregoing problems, chlorohexidin-2-mercaptopyridine-N-oxide is disclosed in JP-A-2004-43421 (“JP-A” means unexamined published Japanese patent application). Although this agent obtained by combining chlorohexidin as a bactericidal disinfectant with 2-mercaptopyridine-N-oxide is improved in bactericidal strength, it still has the simple structure with no substituent on the pyrithione ring.
There are very few pyrithione compounds known to have a substituent on their respective rings. One example of such a compound is described in the Journal of Organic Chemistry, 1995, p. 6706.
In addition, an amino acid moiety-introduced pyrithione derivative is described in the Journal of the American Chemical Society, 1997, p. 6457. Therein, it is stated that the N—O bond is severed in a quantum yield of about 1.0, to produce radicals, when the derivative is irradiated with light of wavelengths in the visible to near ultraviolet region.
Pyrithione compounds, having such a photo-decomposing property, have potential as photo-functional materials. To develop such materials, it is necessary to introduce various substituents into the foregoing simple structure, which can lead to various derivatives, and to impart thereto not only the photo-decomposing property but also a variety of desired properties. To create photo-functional materials in particular, it is necessary to obtain pyrithione derivatives having various substituents. Further, introduction of reactive sections enabling reaction with other compounds, in addition to mere substituents, becomes important for obtaining novel pyrithione derivatives.
On the other hand, microcapsules capable of changing their permeability to some substances by various stimuli have been studied. For instance, microcapsules for encapsulating functional materials, such as medicines, agricultural chemicals, insect repellents, or perfumes, have been offered. As medicine-encapsulated microcapsules, drug delivery systems have been proposed. And slow-release agricultural chemicals have been proposed as agricultural chemical-encapsulated microcapsules. In addition, microcapsules making the most of thermal changes in their permeability to certain substances have been studied for heat-sensitive recording materials. In such microcapsules, color-forming materials (e.g. diazonium salts or leuco dyes) are encapsulated. Alternatively, microcapsules making the most of changes caused in their permeability to certain substances by application of pressure thereto have also been studied, for pressure-sensitive recording materials. In such microcapsules also, color-forming materials (e.g. diazonium salts or leuco dyes) are encapsulated. As microcapsules changing their permeability to certain substances by exposure to light, microcapsules for light- and heat-sensitive recording materials have been proposed. For instance, a description of such microcapsules can be found in JP-A-2000-296675.